Math question: Creating a ratio?

I need to develop a rough ratio based on the following data ...

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I'd like to be able to then enter a number on the left, say 33, and get the corresponding value. Does anyone have experience solving a puzzle like this?

Thank you.

Layne

If all you want is linear interpolation I would use FORECAST.

If you want to get out the equation for a simple linear fit, I would use SLOPE and INTERCEPT rather than LINEST, the answer is the same, but LINEST can be awkward to use.

I quickly copied down your values and tried a trendline in a chart, I note that your data seems to be basically quadratic.

You could use LINEST to get a polynomial solution and actually try to get an equation that fits the data. As mentioned above LINEST can be awkward to use, but it can be worth the hassle if the circumstances dictate.

Mark.

If you are going to use linear interpolation I would select just the points either side of the one you want.

Thus assuming your data is in Columns A and B; Rows 2 to 10:

=FORECAST(A12,OFFSET($B$2,MATCH(A12,A2:A10,1),0,2),OFFSET($A$2,MATCH(A12,A2:A10,1),0,2))

Enter the number to be interpolated into A12

Mark.

PS.
Can anyone think of a neater way to find the addresses of the cells on either side of the required point?
The above equation is aesthetically horrid!